This meta-analysis reviewed 144 studies from 1996 to 2013 using the Beck Depression Inventory–Second Edition. Internal consistency was .89 and test–retest reliability .75. Convergent comparisons were robust across 43 depression instruments. Structural validity supported both one- and two-factor solutions and diagnostic accuracy varied according to sample and criterion cutoff.

Precision is a key facet of test development, with score reliability determined primarily according to the types of error one wants to approximate and demonstrate. This article identifies and discusses several primary forms of reliability estimation: internal consistency (i.e., split-half, KR–20, α), test–retest, alternate forms, interscorer, and interrater reliability.